A metal M readily forms its sulphate `MSO_(4)` which is water soluble. It forms oxide `MO` which becomes inert on heating. It forms insoluble hydroxide which is soluble in `NaOH`. The metal `M` is:

Options

A. Be
B. Ca
C. Sr
D. Mg

Answer

A

Explanation

The metal M is Be because among alkaline earth metal hydroxides, only Be oxide is amphoteric as it dissolves in NaOH:
`Be(OH)_(2)+2NaOHtoNa_(2)BeO_(2)+2H_(2)O`
Moreover, `BeSO_(4)` is water soluble while `Be(OH)_(2)` is water insoluble. BeO becomes inert on heating, its very high melting point (above `2500^(@)C)` and its stability lead to its use as a refractory ad for making sparking plug insulators where its high thermal conductivity and low electrical conductivity are an advantage.